Electronically operated and controlled switch



July 19, 1955 H. J. M CREARY 2,713,515

ELECTRONICALLY OPERATED AND CONTROLLED SWITCH Filed Aug. 19. 1952 INVENTOR HAROLD J. I GREARY 7 HZ/i ATTY Patented July 19, 1955 LECTRGNICALLY OPERATED AND CONTROLLED SWITCH Harold J. McCreary, Lombard, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, III., a corporation of Delaware Application August 19, 1952, Serial No. 305,192

Claims. (Cl. 179-18) This invention relates to an electronically operated and controlled switch of the type which may be used as a selecting switch in a telephone system.

One of the objects of this invention is to provide an electronically controlled and operated switch of simple, effective but inexpensive construction and design.

Another object of said invention is the simplification and reduction in the equipment needed for the operation and control of a switch to thereby reduce the problems inherent in the manufacture of the switches together with the problems inherent in their use and supervision.

A feature of this invention is the electronic means and circuit used to effectuate the stepping of the switch.

Another feature is the electronic arrangement for stopping the switch after it has been stepped. In the particular embodiment disclosed the switch is of a type used as a rotary linefinder switch in a telephone system wherein it would hunt and find one of a number of lines. Its use is not limited to the rotary type but may be easily adapted to a stepping switch having vertical and rotary motion or linear or radial motion. Although a particular embodiment and modification of the invention is described, it should be appreciated that the invention is capable of use with any type selecting switch for controlling the operation of the switch to search for a particular object. This embodiment utilizes a thyratron tube having a self-interrupted electromagnetic stepping means in its plate circuit for stepping the switch wiper. When the switch is idle, the tube is extinguished and the electromagnetic stepping means correspondingly inoperative. At the proper time a circuit is closed in any well known manner to raise the thyratron grid potential to a particular positive value with respect to the cathode to cause the tube to become conductive. The plate circuit of the thyratron is in series with the stepping magnet so that the stepping magnet will not operate unless the thyratron is conducting. The stepping magnet steps the rotary switch wiper in a self-interrupting manner until the switch wiper encounters the desired line. Since the thyratron plate circuit is open each time the wiper is stepped, because of the self-interrupting springs opening at each step, the thyratron is deionized each time the wiper comes to rest on a new contact. On reaching the desired contact a circuit is completed which raises the positive potential of the cathode with respect to the grid so as to prevent the tube from again becoming conductive and thus prevent the further operation of the stepping magnet.

The drawing shows the preferred embodiment of this invention.

Although the preferred embodiment of the invention is herein disclosed and discussed it is to be understood that this invention is not limited to this embodiment but may be adapted to many other uses either in its present form or by slight changes nor does the inventor limit himself to the preferred embodiment.

Having thus described generally the operation of the switch a more detailed study of this invention will be respect to the cathode.

made. The cathode 10 is connected at a point between resistors 9 and 8. The resistor 9 has a value of approximately ohms, the resistor 8 has a value of approximately 820 ohms and the resistor 7 a value of approximately 1000 ohms. This arrangement secures a drop in negative potential sufiieient to raise the cathode 10 to a positive potential of 2 /2 volts which is the equivalent of a 2 /2 volt negative potential on the grid. Negative battery of approximately 48 volts is used. Under these conditions the gas in the tube will not ionize and conduct current. When contacts 1 or 2 are closed in any well known manner (in this example contact 1 will be used for an illustration of the operation), resistors 14 and 15 act as a potentiometer. Resistor 15 being approximately 500,000 ohms and resistor 14 being approximately l0,00t) ohms result in a drop of negative potential which is sufiicient to raise the positive potential of a grid approximately 1 volt and thus cause the gas filled thyratron tube 13 to instantaneously ionize and become conductive to thus complete a circuit for operating stepping magnet 4 as follows: negative battery, resistor 9, cathode 10, plate 12, interrupter contact springs 5, winding of stepping magnet 4 to ground. Stepping magnet 4 operates in a self-interrupted manner to step wiper 3 in any well known manner. Each time the wiper is stepped interrupter contact springs 5 open to break the plate circuit of tube 13 to thereby cause said tube to deionize and stepping magnet 4 to halt operation. As interrupter springs 5 close, the aforementioned circuit is again completed and tube 13 again ionizcs to again operate the stepping magnet 4 to thereby cause wiper 3 to be stepped to its next contact. This process is repeated until wiper 3 encounters contact 16 (as contacts 1 are closed in this particular illustration) in the bank contacts to thus short circuit resistor 7 in the cathode circuit. The new cathode circuit will be as follows: negative battery, resistor 9, resistor 8, conductor 6, wiper 3, contact 16, contact 1 to ground. This approximately doubles the drop in negative potential on the cathode to thus bias the grid more negative with As interrupter springs 5 had opened just before wiper 3 encountered contact 16 the tube deionized as previously described and the new negative bias on the grid 11 prevents the ionization of the gas in the tube when interrupter springs 5 close to thus lock wiper 3 to contact 16.

Thus having described the preferred embodiment of this invention but not limiting myself to the described embodiment what I claim is:

1. In a switch having a wiper, bank contacts accessible thereto and a self-interrupted electromagnet for stepping said wiper, means including a conductive electron tube for causing operation of said electromagnct for stepping said wiper over said contacts, said electron tube having plate and cathode circuits, said plate circuit in series with said electromagnet and interrupted when said electromagnet is interrupted to thereby render said tube non-conductive on each step to successive contacts of said bank contacts, and means rendering said tube conductive after each self-interruption of said electromagnet, for operating said electromagnet, said wiper connected to said cathode for preventing said tube from becoming conductive when said electromagnet has stepped said wiper to a predetermined contact to thereby halt the operation of said electromagnet and further stepping of said wiper.

2. In a switch having a wiper, bank contacts accessible thereto and an electromagnet, having self-interrupting contacts, for stepping said wiper, means for causing the operation of said electromagnet to step said wiper over said bank contacts including a thyratron tube having a plate, grid and cathode circuits, a source of potential, said cathode circuit connected to said source of potential and having a resistor therein for securing a drop of potential to thereby prevent said tube from conducting current, said grid circuit having a potentiometer therein one end of which is connected to said source of potential thereby providing a specific potential on said grid, means for causing a drop in said specific potential on said grid of sufiicient value to cause said tube to conduct current, said plate circuit, self-interrupting contacts and said electromagnet completin a path for said current whereby said electromagnet is operated, said plate circuit interrupted to halt the flow of said current when said selfinterrupting contacts open in conjunction with said electromagnet stepping said wiper to a bank contact, said current flow resumed when said self-interrupting contacts close to again cause said electromagnet to step said wiper, and means including part of said cathode circuit for preventing said resumed current flow after said plate circuit is restored when said wiper encounters a predetermined contact to thereby halt further conduction of current by said tube, operation of said elcctromagnet and further stepping of said wiper.

3. A device such as claimed in claim 2 in which said last means comprises a circuit completed by said wiper and predetermined contact to short circuit part of said resistor in said cathode circuit to thereby prevent said tube from resuming current conduction by increasing the drop of potential on said cathode.

4. in a stepping switch having a wiper, bank contacts accessible thereto, an clectromagnet having self-interrupting contacts for stepping said wiper, a source of potential, a thyratron tube having plate, grid and cathode circuits, a resistance element in said cathode circuit connected on one end to said source of potential and forming a circuit resulting in a drop of potential of sufiicient value as to prevent said tube from operating, another resistance element in said grid circuit connected on one end to said source of potential and forming a circuit on initiation of operation of said switch resulting in a drop of potential of suflicient value as to cause instantaneous operation of said tube, said electromagnet, self-interrupting contacts and plate forming a series circuit for operating said electromagnet to thereby step said wiper over said contacts on operation of said tube, said tube rendered alternately inoperative and operative on opening and closing of said self-interrupting contacts, said wiper connected to a point in said first resistance element and forming a circuit when said wiper encounters a prede termined contact resulting in an increase of potential of such value in said cathode circuit as to prevent reopcration of said tube when said self-interrupting contacts close to thereby halt the operation of said tube, electromagnet and wiper.

5. In a stepping switch including bank contacts and a Wiper associated therewith, a self-interrupted electromagnet for stepping said wiper, means for energizing said electromagnet comprising an electronic valve having plate, grid and cathode circuits, said electromagnet in said plate circuit, a circuit for biasing said grid with respect to said cathode to prevent current flow in said tube when said switch is idle, a source of potential, a circuit completed for said grid including said source of potential on initiation of operation of said switch for changing the bias of said grid with respect to said cathode to cause said valve to conduct current, said electromagnet energized thereby for stepping said wiper and for opening said plate circuit to extinguish said valve and thereby deenergizes itself, said valve thereafter conducting current for again energizing said magnet to step said wiper when said plate circuit is again completed, said source of potential connected to one contact of said bank, said wiper connected to said cathode circuit, and a circuit including said source of potential and part of said cathode circuit completed when said wiper encounters said one contact for changing said grid bias with respect to said cathode to thereby prevent said tube from thereafter becoming conductive to energize said electromagnet for stepping said wiper when said plate circuit is completed.

References Cited in the file of this patent UNITED STATES PATENTS 2,242,776 Clark et al. May 20, 1941 2,354,682 Herbig Aug. 1, 1944 2,502,415 Bray et a1. Apr. 4, 1950 2,616,980 Buckner Nov. 4, I952 

